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Summary: Ctors | Methods | Protected Methods | Inherited Methods

# URLClassLoader

`public class URLClassLoader`
`` `` `extends SecureClassLoader` `implements Closeable`

java.lang.Object
↳ | java.lang.ClassLoader
| ↳ | java.security.SecureClassLoader
|  | ↳ | java.net.URLClassLoader

This class loader is used to load classes and resources from a search path of URLs referring to both JAR files and directories. Any URL that ends with a '/' is assumed to refer to a directory. Otherwise, the URL is assumed to refer to a JAR file which will be opened as needed.

The AccessControlContext of the thread that created the instance of URLClassLoader will be used when subsequently loading classes and resources.

The classes that are loaded are by default granted permission only to access the URLs specified when the URLClassLoader was created.

## Summary

### Public constructors
`URLClassLoader(URL[] urls, ClassLoader parent)` Constructs a new URLClassLoader for the given URLs.
`URLClassLoader(URL[] urls)` Constructs a new URLClassLoader for the specified URLs using the default delegation parent `ClassLoader`.
`URLClassLoader(URL[] urls, ClassLoader parent, URLStreamHandlerFactory factory)` Constructs a new URLClassLoader for the specified URLs, parent class loader, and URLStreamHandlerFactory.

### Public methods
`void` | `close()` Closes this URLClassLoader, so that it can no longer be used to load new classes or resources that are defined by this loader.
`URL` | `findResource(String name)` Finds the resource with the specified name on the URL search path.
`Enumeration<URL>` | `findResources(String name)` Returns an Enumeration of URLs representing all of the resources on the URL search path having the specified name.
`InputStream` | `getResourceAsStream(String name)` Returns an input stream for reading the specified resource.
`URL[]` | `getURLs()` Returns the search path of URLs for loading classes and resources.
`static URLClassLoader` | `newInstance(URL[] urls, ClassLoader parent)` Creates a new instance of URLClassLoader for the specified URLs and parent class loader.
`static URLClassLoader` | `newInstance(URL[] urls)` Creates a new instance of URLClassLoader for the specified URLs and default parent class loader.

### Protected methods
`void` | `addURL(URL url)` Appends the specified URL to the list of URLs to search for classes and resources.
`Package` | `definePackage(String name, Manifest man, URL url)` Defines a new package by name in this ClassLoader.
`Class<?>` | `findClass(String name)` Finds and loads the class with the specified name from the URL search path.
`PermissionCollection` | `getPermissions(CodeSource codesource)` Returns the permissions for the given codesource object.

### Inherited methods
From class `java.security.SecureClassLoader`
`final Class<?>` | `defineClass(String name, byte[] b, int off, int len, CodeSource cs)` Converts an array of bytes into an instance of class Class, with an optional CodeSource.
`final Class<?>` | `defineClass(String name, ByteBuffer b, CodeSource cs)` Converts a `ByteBuffer` into an instance of class `Class`, with an optional CodeSource.
`PermissionCollection` | `getPermissions(CodeSource codesource)` Returns the permissions for the given CodeSource object.
From class `java.lang.ClassLoader`
`void` | `clearAssertionStatus()` Sets the default assertion status for this class loader to `false` and discards any package defaults or class assertion status settings associated with the class loader.
`final Class<?>` | `defineClass(String name, byte[] b, int off, int len, ProtectionDomain protectionDomain)` Converts an array of bytes into an instance of class `Class`, with an optional `ProtectionDomain`.
`final Class<?>` | `defineClass(String name, ByteBuffer b, ProtectionDomain protectionDomain)` Converts a ``ByteBuffer`` into an instance of class `Class`, with an optional `ProtectionDomain`.
`final Class<?>` | `defineClass(byte[] b, int off, int len)` This method is deprecated. Replaced by `defineClass(String, byte[], int, int)`
`final Class<?>` | `defineClass(String name, byte[] b, int off, int len)` Converts an array of bytes into an instance of class `Class`.
`Package` | `definePackage(String name, String specTitle, String specVersion, String specVendor, String implTitle, String implVersion, String implVendor, URL sealBase)` Defines a package by name in this `ClassLoader`.
`Class<?>` | `findClass(String name)` Finds the class with the specified binary name.
`String` | `findLibrary(String libname)` Returns the absolute path name of a native library.
`final Class<?>` | `findLoadedClass(String name)` Returns the class with the given binary name if this loader has been recorded by the Java virtual machine as an initiating loader of a class with that binary name.
`URL` | `findResource(String name)` Finds the resource with the given name.
`Enumeration<URL>` | `findResources(String name)` Returns an enumeration of ``URL`` objects representing all the resources with the given name.
`final Class<?>` | `findSystemClass(String name)` Finds a class with the specified binary name, loading it if necessary.
`Package` | `getPackage(String name)` Returns a `Package` that has been defined by this class loader or any of its ancestors.
`Package[]` | `getPackages()` Returns all of the `Packages` defined by this class loader and its ancestors.
`final ClassLoader` | `getParent()` Returns the parent class loader for delegation.
`URL` | `getResource(String name)` Finds the resource with the given name.
`InputStream` | `getResourceAsStream(String name)` Returns an input stream for reading the specified resource.
`Enumeration<URL>` | `getResources(String name)` Finds all the resources with the given name.
`static ClassLoader` | `getSystemClassLoader()` Returns the system class loader for delegation.
`static URL` | `getSystemResource(String name)` Find a resource of the specified name from the search path used to load classes.
`static InputStream` | `getSystemResourceAsStream(String name)` Open for reading, a resource of the specified name from the search path used to load classes.
`static Enumeration<URL>` | `getSystemResources(String name)` Finds all resources of the specified name from the search path used to load classes.
`Class<?>` | `loadClass(String name, boolean resolve)` Loads the class with the specified binary name.
`Class<?>` | `loadClass(String name)` Loads the class with the specified binary name.
`static boolean` | `registerAsParallelCapable()` Registers the caller as parallel capable.
`final void` | `resolveClass(Class<?> c)` Links the specified class.
`void` | `setClassAssertionStatus(String className, boolean enabled)` Sets the desired assertion status for the named top-level class in this class loader and any nested classes contained therein.
`void` | `setDefaultAssertionStatus(boolean enabled)` Sets the default assertion status for this class loader.
`void` | `setPackageAssertionStatus(String packageName, boolean enabled)` Sets the package default assertion status for the named package.
`final void` | `setSigners(Class<?> c, Object[] signers)` Sets the signers of a class.
From class `java.lang.Object`
`Object` | `clone()` Creates and returns a copy of this object.
`boolean` | `equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void` | `finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>` | `getClass()` Returns the runtime class of this `Object`.
`int` | `hashCode()` Returns a hash code value for the object.
`final void` | `notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void` | `notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String` | `toString()` Returns a string representation of the object.
`final void` | `wait(long timeout, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void` | `wait(long timeout)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void` | `wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.
From interface `java.io.Closeable`
`abstract void` | `close()` Closes this stream and releases any system resources associated with it.
From interface `java.lang.AutoCloseable`
`abstract void` | `close()` Closes this resource, relinquishing any underlying resources.

## Public constructors

### URLClassLoader

    public URLClassLoader (URL[] urls,
                    ClassLoader parent)

Constructs a new URLClassLoader for the given URLs. The URLs will be searched in the order specified for classes and resources after first searching in the specified parent class loader. Any URL that ends with a '/' is assumed to refer to a directory. Otherwise, the URL is assumed to refer to a JAR file which will be downloaded and opened as needed.

If there is a security manager, this method first calls the security manager's `checkCreateClassLoader` method to ensure creation of a class loader is allowed.

Parameters
`urls` | `URL`: the URLs from which to load classes and resources
`parent` | `ClassLoader`: the parent class loader for delegation

Throws
`SecurityException` | if a security manager exists and its `checkCreateClassLoader` method doesn't allow creation of a class loader.
`NullPointerException` | if `urls` is `null`.

See also:

- `SecurityManager.checkCreateClassLoader()`

### URLClassLoader

    public URLClassLoader (URL[] urls)

Constructs a new URLClassLoader for the specified URLs using the default delegation parent `ClassLoader`. The URLs will be searched in the order specified for classes and resources after first searching in the parent class loader. Any URL that ends with a '/' is assumed to refer to a directory. Otherwise, the URL is assumed to refer to a JAR file which will be downloaded and opened as needed.

If there is a security manager, this method first calls the security manager's `checkCreateClassLoader` method to ensure creation of a class loader is allowed.

Parameters
`urls` | `URL`: the URLs from which to load classes and resources

Throws
`SecurityException` | if a security manager exists and its `checkCreateClassLoader` method doesn't allow creation of a class loader.
`NullPointerException` | if `urls` is `null`.

See also:

- `SecurityManager.checkCreateClassLoader()`

### URLClassLoader

    public URLClassLoader (URL[] urls,
                    ClassLoader parent,
                    URLStreamHandlerFactory factory)

Constructs a new URLClassLoader for the specified URLs, parent class loader, and URLStreamHandlerFactory. The parent argument will be used as the parent class loader for delegation. The factory argument will be used as the stream handler factory to obtain protocol handlers when creating new jar URLs.

If there is a security manager, this method first calls the security manager's `checkCreateClassLoader` method to ensure creation of a class loader is allowed.

Parameters
`urls` | `URL`: the URLs from which to load classes and resources
`parent` | `ClassLoader`: the parent class loader for delegation
`factory` | `URLStreamHandlerFactory`: the URLStreamHandlerFactory to use when creating URLs

Throws
`SecurityException` | if a security manager exists and its `checkCreateClassLoader` method doesn't allow creation of a class loader.
`NullPointerException` | if `urls` is `null`.

See also:

- `SecurityManager.checkCreateClassLoader()`

## Public methods

### close

    public void close ()

Closes this URLClassLoader, so that it can no longer be used to load new classes or resources that are defined by this loader. Classes and resources defined by any of this loader's parents in the delegation hierarchy are still accessible. Also, any classes or resources that are already loaded, are still accessible.

In the case of jar: and file: URLs, it also closes any files that were opened by it. If another thread is loading a class when the `close` method is invoked, then the result of that load is undefined.

The method makes a best effort attempt to close all opened files, by catching `IOException`s internally. Unchecked exceptions and errors are not caught. Calling close on an already closed loader has no effect.

Throws
`IOException` | if closing any file opened by this class loader resulted in an IOException. Any such exceptions are caught internally. If only one is caught, then it is re-thrown. If more than one exception is caught, then the second and following exceptions are added as suppressed exceptions of the first one caught, which is then re-thrown.
`SecurityException` | if a security manager is set, and it denies `RuntimePermission``("closeClassLoader")`

### findResource

    public URL findResource (String name)

Finds the resource with the specified name on the URL search path.

Parameters
`name` | `String`: the name of the resource

Returns
`URL` | a `URL` for the resource, or `null` if the resource could not be found, or if the loader is closed.

### findResources

    public Enumeration<URL> findResources (String name)

Returns an Enumeration of URLs representing all of the resources on the URL search path having the specified name.

Parameters
`name` | `String`: the resource name

Returns
`Enumeration<URL>` | an `Enumeration` of `URL`s If the loader is closed, the Enumeration will be empty.

Throws
`IOException` | if an I/O exception occurs

### getResourceAsStream

    public InputStream getResourceAsStream (String name)

Returns an input stream for reading the specified resource. If this loader is closed, then any resources opened by this method will be closed.

The search order is described in the documentation for `ClassLoader.getResource(java.lang.String)`.

Parameters
`name` | `String`: The resource name

Returns
`InputStream` | An input stream for reading the resource, or `null` if the resource could not be found

### getURLs

    public URL[] getURLs ()

Returns the search path of URLs for loading classes and resources. This includes the original list of URLs specified to the constructor, along with any URLs subsequently appended by the addURL() method.

Returns
`URL[]` | the search path of URLs for loading classes and resources.

### newInstance

    public static URLClassLoader newInstance (URL[] urls,
                    ClassLoader parent)

Creates a new instance of URLClassLoader for the specified URLs and parent class loader. If a security manager is installed, the `loadClass` method of the URLClassLoader returned by this method will invoke the `SecurityManager.checkPackageAccess` method before loading the class.

Parameters
`urls` | `URL`: the URLs to search for classes and resources
`parent` | `ClassLoader`: the parent class loader for delegation

Returns
`URLClassLoader` | the resulting class loader

Throws
`NullPointerException` | if `urls` is `null`.

### newInstance

    public static URLClassLoader newInstance (URL[] urls)

Creates a new instance of URLClassLoader for the specified URLs and default parent class loader. If a security manager is installed, the `loadClass` method of the URLClassLoader returned by this method will invoke the `SecurityManager.checkPackageAccess` before loading the class.

Parameters
`urls` | `URL`: the URLs to search for classes and resources

Returns
`URLClassLoader` | the resulting class loader

Throws
`NullPointerException` | if `urls` is `null`.

## Protected methods

### addURL

    protected void addURL (URL url)

Appends the specified URL to the list of URLs to search for classes and resources.

If the URL specified is `null` or is already in the list of URLs, or if this loader is closed, then invoking this method has no effect.

Parameters
`url` | `URL`: the URL to be added to the search path of URLs

### definePackage

    protected Package definePackage (String name,
                    Manifest man,
                    URL url)

Defines a new package by name in this ClassLoader. The attributes contained in the specified Manifest will be used to obtain package version and sealing information. For sealed packages, the additional URL specifies the code source URL from which the package was loaded.

Parameters
`name` | `String`: the package name
`man` | `Manifest`: the Manifest containing package version and sealing information
`url` | `URL`: the code source url for the package, or null if none

Returns
`Package` | the newly defined Package object

Throws
`IllegalArgumentException` | if the package name duplicates an existing package either in this class loader or one of its ancestors

### findClass

    protected Class<?> findClass (String name)

Finds and loads the class with the specified name from the URL search path. Any URLs referring to JAR files are loaded and opened as needed until the class is found.

Parameters
`name` | `String`: the name of the class

Returns
`Class<?>` | the resulting class

Throws
`ClassNotFoundException` | if the class could not be found, or if the loader is closed.
`NullPointerException` | if `name` is `null`.

### getPermissions

    protected PermissionCollection getPermissions (CodeSource codesource)

Returns the permissions for the given codesource object. The implementation of this method first calls super.getPermissions and then adds permissions based on the URL of the codesource.

If the protocol of this URL is "jar", then the permission granted is based on the permission that is required by the URL of the Jar file.

If the protocol is "file" and there is an authority component, then permission to connect to and accept connections from that authority may be granted. If the protocol is "file" and the path specifies a file, then permission to read that file is granted. If protocol is "file" and the path is a directory, permission is granted to read all files and (recursively) all files and subdirectories contained in that directory.

If the protocol is not "file", then permission to connect to and accept connections from the URL's host is granted.

Parameters
`codesource` | `CodeSource`: the codesource

Returns
`PermissionCollection` | the permissions granted to the codesource

Throws
`NullPointerException` | if `codesource` is `null`.

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